In the manufacture of microstructures, for example microelectro-mechanical structures (MEMS), gas-phase etching processes are used to remove sacrificial (i.e. unwanted) areas of material so as to leave behind the remaining material which constitutes the desired structure.
For example, xenon difluoride (XeF2) is commonly used to remove sacrificial areas of silicon in the manufacture of MEMS. XeF2 demonstrates high selectivity and has a relatively high etch rate when etching silicon. However, for the manufacture of more complex and higher quality MEMS devices, it is desirable to improve the selectivity of XeF2 processes over conventional techniques.